1. Field of the Invention
The present invention relates to a printed circuit board.
2. Description of the Background Art
A large number of flexible printed circuit boards (see JP2002-111138A, for example) are used in electronic equipment, electric equipment and the like. Hereinafter, the flexible printed circuit board is abbreviated as the printed circuit board.
FIG. 5 is a perspective view showing the appearance of the conventional printed circuit board. The printed circuit board 700 shown in FIG. 5 includes a base insulating layer 701 and a long-sized conductor pattern 702 provided on the base insulating layer 701. In addition, a cover insulating layer (not shown) is formed on the base insulating layer 701 so as to cover the conductor pattern 702.
The printed circuit board 700 having such a configuration has excellent flexibility, and can be easily folded at an arbitrary position as shown in FIG. 5. Therefore, conventionally, the printed circuit board 700 has been effectively used in a bending portion such as a hinge of electronic equipment.
When part of the printed circuit board 700 is folded into two as shown in FIG. 5, however, part of the conductor pattern 702 faces another part of the conductor pattern 702 in a vertical direction in the folded region. This forms a large capacitive component between the parts of the conductor pattern 702 facing each other. In this case, a difference in the characteristic impedance of the conductor pattern 702 is caused between the region in which the parts of the conductor patterns 702 face each other and the other region. As a result, transmission efficiency of electrical signals is reduced in the printed circuit board 700.